The grill element which is the subject of the present invention very broadly concerns an apparatus for heat exchange between a solid in a divided condition at a very high temperature, and a fluid.
The invention also concerns a method of preheating a fluid by heat exchange with a divided solid which is at a very high temperature, in which solid particles or grains are dropped onto a grill element, through the openings in which a fluid is injected in a counter-flow mode. The method according to the invention is applied in particular to the construction of an apparatus for preheating the air which is introduced into a rotary furnace such as a cement works furnace, in order to burn the fuel.
It is known for the air which is used as an oxidant in cement works furnaces to be preheated by heat exchange with the clinker which is discharged at the lower end of such furnaces, at a temperature on the order of 1400.degree. C. The clinker is generally in the form of grains with a mean diameter on the order of from 20 to 30 mm and it drops on to the grill elements which have holes therethrough, through which the air is injected in a counter-flow mode. That air is heated by contact with the grains of clinker and is thus raised to a temperature on the order of 1200.degree. to 1400.degree. C. The grill elements are fixed or movable. Each movable element is secured in position by a catch or latching device with a mechanical carrying means which transmits thereto an alternating movement to cause the layer of clinker to be progresively displaced along its surface. Thus, the clinker goes from one grill element to another along a discharge passage, undergoing progressive cooling as it does so. At the end of the passage, the clinker, being sufficiently cooled by the flow of air, is discharged to the crushing means.